This invention relates to solid-state photodector structures which can be integrated on the same chip with MOSFET circuits, or on the same chip with CCD circuits, or on the same chip with both MOSFET and CCD circuits.
Silicon MOSFET scanned and CCD scanned solid state photodetector arrays are well reported in the literature and are commercially available. Reference may be made, for example, to Fairchild Technical Data Sheet, "CCD 122/142, 1728/2048 Element Linear Image Sensor Charge Coupled-Device", Mountain View, Calif., April 1979 (reference 1a) and to Reticon product summary "Solid-State Image Sensors, 64 to 1872 Elements RC 1728 H, RC 1024 H", Reticon Corp., Sunnyvale, Calif., 1976 (reference 1b). Such photodetector arrays incorporate either photodiodes or photogates as their photoelements. Such photoelements which operate in the integration mode (see Savvas G. Chamberlain, "Photosensitivity and Scanning of Silicon Image Detector Arrays", IEEE Journal of Solid-State Circuits, Vol. SC-4, No. 6, pp 333-342, December 1969 -reference 2a) have a detecting light intensity dynamic range of from about 200 to a maximum of about 5000.
A normal silicon photodiode operating in the solar cell mode, i.e., photovoltaic mode (see Aldert Van Der Ziel, "Solid-State Physical Electronics", Third Edition, Prentice Hall, 1976 --reference 2b) would have a detecting light intensity dynamic range of greater than 5000. However, a silicon photodiode operating in the photovoltaic mode is essentially forward biased and cannot be integrated easily on the same silicon chip as MOSFET scanning and readout shift registers, if standard MOSFET silicon technology is used. Moreover, a silicon solar cell cannot be integrated on the same silicon chip with CCD readout and scanning shift registers if standard CCD/MOSFET silicon technology is used.
In laser optical communications and other electronic imaging applications, e.g., document readers, facsimile (telecopier) there is a need for a photodetector structure having a wide light intensity dynamic range, preferably greater than 10.sup.6, which can be integrated easily on a single silicon chip to form linear and area photodetector arrays. On the same chip with the photodetector arrays would be MOSFET and/or CCD shift registers for scanning.